This invention relates in general to vehicle frame assemblies. In particular, this invention relates to a modular vehicle frame assembly which includes up to three hollow, U-shaped cradle frame subassemblies connected by a pair of open channel side rails.
Virtually all land vehicles in common use, such as automobiles and trucks, include a frame which serves as a platform upon which the remainder of the vehicle is built. Many vehicle frame structures are known in the art. Most of these known vehicle frame structures are formed from a number of individual metallic components which are permanently joined together. For example, a typical perimeter vehicle frame assembly is composed of a pair of longitudinally extending side rails which are joined together at the front by a forward cross member, at the rear by a rearward cross member, and at intermediate locations by one or more intermediate or auxiliary cross members. The cross members not only connect the two side rails together, but also provide desirable lateral and torsional rigidity to the vehicle frame assembly. In some vehicle frame assemblies, the side rails and cross members are formed from open channel structural members, i.e., structural members which have a noncontinuous cross-sectional shape (C-shaped channel members, for example). In other vehicle frame assemblies, the side rails and cross members are formed from closed channel structural members, i.e., structural members which have a continuous cross-sectional shape (box-shaped channel members, for example). Regardless of the specific structure of the structural members, the side rails and cross members, once joined together, form a rigid frame for supporting the remaining portions of the vehicle thereon.
Typically, the cross members extend transversely relative to the two parallel side rails, and the ends of the cross members are permanently secured to the side rails to form a generally rectangular vehicle frame assembly. The cross members are usually secured to the side rails by initially welding brackets to the side rails, then connecting the ends of the cross rails to the brackets by bolts or rivets. The brackets not only support the cross member on the side rails, but also prevent lateral movement of the cross members relative to the side rails. Once the vehicle frame assembly is completed, the remaining components of the vehicle, including the body, drive train, and suspension, can be mounted thereon in a known manner. The side rails for a full perimeter frame structure are typically manufactured to a predetermined length which is appropriate for the particular vehicle. The side rails can be formed as a single member which extends most or all of the length of the vehicle. Alternatively, the side rails can be formed from two or more pieces which are overlapped and then bolted, welded, riveted, or otherwise secured together to form the desired length of the side rail. Once the side rails are made to length, the full perimeter frame is assembled by joining the appropriate number of cross members to the side rails to form a single structure.
It is known that the length of the side rails will vary with different models of vehicles. In addition, it is likely that the number of cross members, and the attachment points of such cross members to the side rails, will also vary for different models of vehicles. In order to produce several different models of full perimeter frame structures on an assembly line, a significant inventory of various side rails and cross members needs to be kept on hand. Maintaining a large inventory of frame assembly parts is both costly and inefficient. Ideally, it would be desirable to provide a modular full perimeter vehicle frame assembly which includes both interchangeable subassemblies and subassemblies which are easily modified for use with a specific vehicle. The use of such a modular vehicle frame assembly would allow more design flexibility while decreasing the amount of inventory required to produce several different models of vehicles.